Glycolysis and the hexose monophosphate shunt are the pathways of central carbohydrate metabolism common to almost all cells. Our studies of their biochemical genetics in Escherichia coli are directed to two types of problems. (1) The mechanism of gene expression of these constitutive enzymes. (2) The use of mutants to further our understanding of central metabolism and its control. The work for which support is here requested is mainly enzymological. One project is the characterization of altered phosphofructokinase in some mutants; at least three genes seem to affect this activity, and certain mutants have an enzyme which is not allosteric. Another project is to ascertain whether mutations affecting the amount of glucose 6-P dehydrogenase also affect its structure. A third project is to use some of the mutants to clarify the role of the hexose monophosphate shunt in reduced NADP formation.